Two-fraction model of initial sediment motion in gravel-Bed rivers     

PR Wilcock 《Science (New York, N.Y.)》1998,280(5362):410-412

The prediction of sediment transport in gravel-bed rivers is essential to the management of land, water, and ecological resources in mountain regions. Dividing the bed sediment into two populations-sand and gravel-permits realistic and useful predictions of the onset of sediment transport. The critical flow initiating grain motion decreases rapidly with sand content over the transition from a gravel-framework bed to a sand-matrix bed. The two-fraction model provides a simple means of forecasting the movement of excess fine sediment supply. The model also helps to explain the development of the abrupt gravel-sand transition commonly observed in natural rivers.  相似文献   

Measuring the spin polarization of a metal with a superconducting point contact     

Soulen Jr RJ  JM Byers  MS Osofsky  B Nadgorny  T Ambrose  SF Cheng  Broussard C T Tanaka PR  J Nowak  JS Moodera  A Barry  JMD Coey 《Science (New York, N.Y.)》1998,282(5386):85-88

A superconducting point contact is used to determine the spin polarization at the Fermi energy of several metals. Because the process of supercurrent conversion at a superconductor-metal interface (Andreev reflection) is limited by the minority spin population near the Fermi surface, the differential conductance of the point contact can reveal the spin polarization of the metal. This technique has been applied to a variety of metals where the spin polarization ranges from 35 to 90 percent: Ni0.8Fe0.2, Ni, Co, Fe, NiMnSb, La0.7Sr0.3MnO3, and CrO2.  相似文献   

Cloning and sequencing of the ovine gamma-interferon gene   总被引：1，自引：0，他引：1  

AJ RADFORD  ALM HODGSON  JS ROTHEL  PR WOOD 《Australian veterinary journal》1991,68(3):82-84

Cytokines are major modulators of the immune system of all animals. The cloning and expression of recombinant cytokine genes have permitted the analysis of their immune function and role in the control of the immune response to disease and vaccination. While human, murine, and bovine genes have been cloned and sequenced, the cloning of ovine cytokine genes has not yet been reported. As sheep are of dominant economic importance to the Australian farming industry, it is of significance to clone and express these genes to facilitate the development of new and better vaccines and pharmaceuticals. We have initially selected ovine gamma-interferon (gamma-IFN) as a target cytokine gene. By the use of the polymerase chain reaction (PCR), using primers based on the bovine gamma-interferon sequence, we have amplified the ovine gamma-interferon gene from crude messenger RNA extracted from lymphocytes. After cloning and DNA sequencing the gene, we found that ovine gamma-IFN is 93% identical to bovine gamma-IFN in amino acid sequence. This result indicates that the PCR method will be a rapid and efficient means for cloning other ovine cytokine genes.  相似文献   

Identification of galegine, an isoprenyl guanidine, as the toxic principle of Schoenus asperocarpus (poison sedge)     

CR HUXTABLE  PR DORLING  SM COLEGATE 《Australian veterinary journal》1993,70(5):169-171

SUMMARY An Isoprenyl guanldine, galegine, was isolated from the Western Australian sedge Schoenus asperocarpus (Cyperaceae). Synthetic galegine was shown to reproduce the clinical and pathological features of poisoning by this plant. Preliminary results suggest that the massive thoracic effusion observed in sedge poisoning is the result of a direct effect on pulmonary vascular permeability.  相似文献   

The Aerobiological Pathway of a Fish Pathogen: Survival and Dissemination of Aeromonas salmonicida in Aerosols and its Implications in Fish Health Management     

Gregory A.  Wooster Paul R.  Bowser 《Journal of the World Aquaculture Society》1996,27(1):7-14

The aerobiological (aerosol) pathway of Aeromonas salmonicida subspecies salmonicida (ATCC 33658) was investigated. Results indicate that viable A. salmonicida can travel as an aerosol/droplet spray at least 104.1 cm (limits of the test chamber used) when carried by air currents. Additionally, viable A. salmonicida was recovered from water exposed to an experimentally generated aerosol/droplet spray of A. salmonicida downwind from the contaminant source. It is possible that viable bacterial aquatic animal pathogens can be spread via the airborne route. This possible route of pathogen introduction could effect current management or system designs, especially when aquaculture systems consist of tanks in close proximity.  相似文献   

Effect of water temperature on the clinical outcome of infection with Edwardsiella ictaluri in channel catfish   总被引：1，自引：0，他引：1  

R Francis-Floyd  M H Beleau  P R Waterstrat  P R Bowser 《Journal of the American Veterinary Medical Association》1987,191(11):1413-1416

Channel catfish fingerlings (mean body weight, 19 +/- 3 g each) were given intraperitoneal inoculations of Edwardsiella ictaluri suspensions of 10(4), 10(5), or 10(6) bacteria. Control fish were inoculated intraperitoneally with sterile 0.85% NaCl solution. Ten-day trials were conducted at water temperatures of 17, 21, 23, 25, 28, and 32 C. Differences in mortality between E ictaluri-infected fish and fish used as controls were observed at water temperatures of 23, 25, and 28 C, but not at temperatures of 17, 21, and 32 C. Clinical signs and lesions induced by intraperitoneal inoculation of E ictaluri were comparable with those found with the intestinal form of the natural disease. The characteristic erosion of skin and muscle overlying the skull, known as the "hole-in-the-head" lesion, was not observed. A given fish may be susceptible to infection at any water temperature, but a population is at risk when water temperatures are in the 22 to 28 C range.  相似文献   

Associations between liveweight,body condition score and previous reproductive outcomes,and the risk of ewes bred at 18-months of age being dry at docking     

KJ Griffiths  AL Ridler  C Heuer  RA Corner-Thomas  PR Kenyon 《New Zealand veterinary journal》2018,66(6):290-296

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Sperm Morphology Assessment in Captive Neotropical Primates          下载免费PDF全文

WF Swanson  RR Valle  FM Carvalho  PR Arakaki  AZ Rodas‐Martínez  JAPC Muniz  M García‐Herreros 《Reproduction in domestic animals》2016,51(4):623-627

The main objective of this study was to evaluate sperm morphology in four neotropical primate species to compare the sperm morphological traits and the sperm morphometric parameters as a basis for establishing normative sperm standards for each species. Data from 80 ejaculates collected from four primate species, Callithrix jacchus, Callimico goeldii, Alouatta caraya and Ateles geoffroyi, were analysed for detection of sperm morphological alterations using subjective World Health Organization (WHO‐2010) standards and Sperm Deformity Index (SDI) criteria, objective computer‐assisted sperm morphometry analysis (CASMA) and subpopulation sperm determination (SSD) methods. There were multiple differences (p < 0.01) observed among primate species in values obtained from WHO‐2010, SDI, CASMA and SSD sperm analysis methods. In addition, multiple significant positive and negative correlations were observed between the sperm morphological traits (SDI, Sperm Deformity Index Head Defects, Sperm Deformity Index Midpiece Defects, Sperm Deformity Index Tail Defects, Normal Sperm, Head Defects, Midpiece Defects and Tail Defects) and the sperm morphometric parameters (SSD, Area (A), Perimeter (P), Length (L), Width (W), Ellipticity, Elongation and Rugosity) (p ≤ 0.046). In conclusion, our findings using different evaluation methods indicate that pronounced sperm morphological variation exists among these four neotropical primate species. Because of the strong relationship observed among morphological and morphometric parameters, these results suggest that application of objective analysis methods could substantially improve the reliability of comparative studies and help to establish valid normative sperm values for neotropical primates.  相似文献   

A Reply to Professor Hathaway     

Bowser EA 《Science (New York, N.Y.)》1893,21(527):134-135

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Experimental Infection of Four Aquacultured Species with Viral Hemorrhagic Septicemia Virus Type IVb     

Geoffrey H. Groocock  Stephen A. Frattini  Emily R. Cornwell  Laura L. Coffee  Gregory A. Wooster  Rodman G. Getchell  Paul R. Bowser 《Journal of the World Aquaculture Society》2012,43(4):459-476

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